Nisan comments on Robust Cooperation in the Prisoner's Dilemma - Less Wrong

69 Post author: orthonormal 07 June 2013 08:30AM

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Comment author: Nisan 17 September 2013 12:52:08AM 1 point [-]

That was a response to

Is there a good (easy) reference for the statement about quining in PA

Comment author: magfrump 09 October 2013 05:34:15PM 0 points [-]

Let me rephrase my question, then, because the diagonal lemma seems clear enough to me. What is a good definition of quining? The term isn't used at all either in the article you linked or it the page on self-reference, which surprised me.

Comment author: Nisan 09 October 2013 08:13:19PM 5 points [-]

Oh! Ok, a quine is

a computer program which takes no input and produces a copy of its own source code as its only output.

If you understand how to write a quine and you understand how the diagonal lemma works, you will find that the two concepts are basically the same thing. "Quine" is more of a computer science term than a mathematical logic term, so not all expositions of Gödel's incompleteness theorem will mention "quining".